Water flow apparatus

ABSTRACT

A guttering system for water drainage of roofs and buildings. The gutter system comprising a first elongate covered channel member capable of carrying water flow in a first direction and at least a second elongate covered channel positioned above or below said first elongate covered channel, capable of transporting water in a same said direction of water flow.

RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 13,148,165 filed Sep. 15, 2011, which in turn is aNational Stage Application of PCT/GB09/00336 filed Feb. 6, 2009. Thedisclosure of these prior references is herein incorporated by referencein its entirety.

FIELD OF THE INVENTION

The present invention relates to an improved rain water collectionsystem.

BACKGROUND TO THE INVENTION

Gutters are predominantly designed to channel rainwater from roofs andbuildings to various water drainage systems to avoid accumulation ofhigh volumes of water which can cause flooding and water damage tobuilding and roofing materials.

Various types of gutter systems are well known in the art. FIG. 1depicts one of the simplest forms of gutter system know in the art. Thegutter comprises a narrow open trough (101), which collects rainwaterfrom the roof of a building. The gutter is configured to have a wateroutlet at a first end (102) at which there is attached a downpipe (103)down which water is diverted away from the building, typically into adrain (not shown).

In a conventional gutter system as shown in FIG. 1, the rate of waterflow is dictated by the amount of rainwater that falls on the roof viarainfall, and by gravity pulling water down the drainpipe. In manygutter systems, the trough is inclined so that water flows by force ofgravity, by locating a first end of the trough at a lower position to asecond end, thus so that water flow is directed towards drain pipe(103).

drainage system in a given time. However, there is an inherent limit inthe number of drainage outlets that can be inserted into a given lengthof gutter channel. This also leads to the need for multiple downpipeswhich is a disadvantageous as it can lead to obstruction issues forother structural building works and access points.

Another major problem is that the flow rates can only be increased to acertain level due to the constraints of gravitational pull. This isespecially a problem during heavy rainfall. If the flow rate in thegutter is not the same or greater than the flow rate of water enteringthe gutter system, then the gutter system will overflow.

The problems mentioned above have led to the development of knownsiphonic drainage systems. Siphonic drainage systems typically used inbuildings having roofs with a large surface area, for example airports,warehouses, stadiums and the like.

Referring to FIG. 2 herein, there is shown one example of a knownsiphonic drainage system comprising a plurality of siphonic inlets and aconnecting collection pipe. Siphonic systems work by havingsubstantially closed pipe systems where by the level of water enteringthe system is manipulated by the size of the water system (110, 114,112) and/or the use of baffle plates at water inlets (111) to restrictthe air entering the drainage system. When a system becomes full ofwater and therefore void of air, the action of water dropping down thedownpipe (112) will cause a negative pressure to form at a top end ofthe downpipe (113). This negative pressure can be utilised to ‘suck’water along the water pipe (114) installed horizontally connecting thewater outlets at a higher level.

By using siphonic drainage processes, the rate of water flow issignificantly increased relative to simple gravity dependent systems,and the need for multiple downpipes is reduced, because each downpipecarries water at a higher flow rate.

However, in pipe based siphonic systems. The pipe work is positionedinside the building adjacent or under the roof. Under high rainfallrates, overflow of the open channel into the building can occur. This isoften incorrectly attributed to leaking joints, leading to unnecessarymaintenance which does not actually solve the problem of overflow overthe sides of the channel.

For large buildings, one face of the building can span over 300 metreslong.

Drainage systems are required to run the whole length of such buildingfaces. However, known drainage systems are unmanageable and impracticalat distances of more than approximately 200 metres long due to theeffective balance and operation of the siphonic action limitation abovethis distance.

Referring to FIG. 3 herein, there is shown a shown gutter assembly asdisclosed in international patent application WO/2007/080380. FIG. 3shows a gutter assembly (302) comprising an elongate gutter (304) forreceiving water and defining a primary water transport channel (310) anda secondary water transport channel (312) is disclosed. The primarywater transport channel (310) is connected to a drainage downpipe (338)and vortex reduction members (324) reduce formation of vortices in thevicinity of primary water inlets (316) of the primary water transportchannel (310). When sufficient water flows into the gutter (304), theprimary water transport channel (310) fills with water to become free ofair to enable water to be transported along the channel (310) by meansof suction in the drainage downpipe (338).

An advantage of this system is that the predominantly closed systemenables all water transport channels to be provided externally to abuilding. This is an advantage because the risk of water leaking fromthe gutter system into the building is minimised.

FIG. 3 shows two transport channels, (310) and (312) of which the twochannels lie side by side and where at least one part of a saidtransport channel has an increasing cross-sectional area in a directiontoward a first water outlet, whereas a second transport channel has anincreasing cross-sectional area in a direction toward a second wateroutlet. A major disadvantage of this invention is that the shape of thetapered water transport channels means that the water transport channelshave to be placed so that the first water outlet and the second wateroutlet have to be placed at opposite ends to each other. This means thatthe water flow in each of the separate channels flows in oppositedirections to each other. As a result, downpipes and drainage means areneeded at two different outlets of the gutter system, one at each end.

The water transport channels disclosed in international patentapplication WO/2007/080380 are disadvantageous as they have to be shapedin a way that they not conventionally symmetrical, therefore the watertransport channels will undergo tessellation problems with the rest of abuilding development if an odd number of water transport channels areincorporated into the gutter assembly.

Referring to FIG. 4 herein, there is illustrated schematically in planview from above a section of a roof of a building, fitted with sixseparate runs of guttering of a type as disclosed in WO/2007/080380.First and second roof sections (401, 402), in this case each having atriangular pitched roof, are fitted with first to sixth elongateguttering systems (403-408) respectively, running parallel to thevalleys of the pitched roofs. A maximum span of building, which can bedrained using a system disclosed in WO/2007/080380 between downpipes isapproximately 200 metres. Where a roof span of more than 200 metersneeds to be drained, for example the 300 meter span as shown on FIG. 4herein, this can be accommodated by fitting two 150 metre length guttersend to end, for example (407, 408). Since each run of gutter requires adownpipe at each end, this means that a drainage point must be installedinto the ground, both at each side of the building (409, 410) and at thecentre of the building (411, 412). Consequently, drainage points andunderground drains (413, 414) need to be laid underneath the concreteslab foundation and along the centre of the building to drain the waterto either one or both ends of the building. Additionally, there will bea plurality of downpipes (415 420) which need to run vertically down thecentre of the building, from the roof to the drains in the floor slabwhich limit the amount of an obstructed open free space within thebuilding.

Where guttering is being fitted to an existing building, the drainagepoints and underground drains may have not been already providedunderneath the concrete slab. Fitting those underground drains anddrainage points can be a laborious and disruptive procedure, involvingbreaking the concrete slab foundation of the building, and the dampproofing course underneath the building and digging a trench in order toretrospectively fit the necessary drainage points and pipes to the edgeof the building.

On a building with a wide fascia, a result of having a two-directionalwater flow 420 and 421) means that there would be a water downpipelocated at each side or end of the building as well as a down pipelocated toward the middle of the building. The non-centralised drainagesection of a known gutter assembly causes problems with the regulationof drainage, as well as increasing obstructions.

SUMMARY OF THE INVENTION

Embodiments of the present invention aim to provide an improved guttersystem which can have multiple water transport channels whereby thewater is directed to a single drainage position. Furthermore, theproposed system may be utilised to incorporate a siphonic process so asto achieve an overall increased flow rate relative to a simple gravitybased gutter system.

According to a first aspect there is provided a guttering systemcomprising:

a first elongate covered channel member capable of carrying waterflowing in a first direction;

at least a second elongate covered channel member positioned above orbelow said first elongate covered channel member, said second channelcapable of transporting carrying water flowing in said first direction.

In use, the first channel may provide primary drainage under normalrainfall conditions, and the second channel may provide secondary oroverflow drainage under conditions of abnormal or increased rainfallconditions.

Preferably said first and/or second channel has a cross sectional areawhich increases in the direction of water flow. This may promote theonset of siphonic operation of the channel(s), thereby increasing theirdrainage capacity.

Preferably, said first and/or second channel is of a substantiallyconstant height along its full length. This may provide convenience ofmanufacture of the gutter.

Preferably, said gutter comprises:

a first water inlet positioned at a first end of said gutter forallowing water to enter said first channel;

a first water outlet positioned at a second end of said gutter fordraining water from said first channel;

a second water inlet positioned at said first end of said gutter forallowing water to enter said second channel; and

a second water outlet positioned at said second end of said gutter fordraining said second channel.

The inlets may be provided with at least one vortex reducing means forminimizing vortex formation in and around said inlets.

Preferably, said first channel is formed within a first cavity, saidfirst cavity having a substantially trapezoidal cross sectional area asviewed in a direction perpendicular to a main length of said gutter;

said first channel is defined by at least one elongate tapered insertfitted inside said first cavity;

said second channel is formed within a second cavity, said second cavityhaving a substantially trapezoidal cross sectional area as viewed in adirection perpendicular to a main length of said gutter; and

said second channel is defined by at least one tapered insert memberfitted within said second cavity.

Having substantially trapezoidal shaped cavities enables a trough shapedgutter to be made in a single operation, with the cavities being formedby fitting first and second covers between the sides of the trough, withthe channels being formed between single insert members or pairs ofinsert members fitted within each cavity.

said first and/or second channel may have a substantially rectangularcross sectional area in a direction perpendicular to any main length ofsaid gutter.

According to a second aspect there is provided a gutter systemcomprising:

an elongate trough having a floor, a first elongate upright side walland a second elongate upright side wall;

an elongate cover member spaced apart from said floor and extendingbetween said upright side walls, and closing off an upper part of saidtrough at a first height, so as to define an enclosed cavity therebetween;

characterised by:

a single enclosed channel being provided across said trough between saidfloor and said cover member and extending along a length of said trough;

a water inlet for allowing water to enter said channel; and

a water outlet for allowing water to drain from said channel;

said inlet and outlet being provided spaced apart from each other alonga length of the gutter, such that water entering said channel via saidinlet passes through said channel to said outlet.

said enclosed channel having a variable cross sectional area in adirection transverse to a main length of said trough, and whichincreases along a main length of said trough in a direction from saidinlet to said outlet, so as to be relatively increased at said outletcompared to at said inlet.

said gutter may comprise at least one insert member located between saidfloor and said cover, said insert member having a cross sectional areain a direction perpendicular to its main length which varies betweenfirst and second ends of said insert member.

Preferably the gutter comprises a pair of insert members located betweensaid floor and said cover, at least one of said insert members beingtapered, wherein said channel is positioned between said pair of insertmembers.

Preferably, said gutter comprises a second elongate cover memberpositioned above said first cover member, so as to define a secondcavity between said second cover, said first cover and said first andsecond upright side walls;

a single second enclosed channel being provided across said troughbetween said first cover, said second cover and said first and secondupright side walls, said second channel extending along a length of saidtrough;

said second enclosed channel having a variable cross sectional area in adirection transverse to a main length of said trough, and whichincreases along a main length of said trough in a same direction as saidfirst channel increases in cross sectional area.

Preferably, the gutter further comprises:

a second water inlet for allowing water to enter said second channel;and

a second water outlet for allowing water to drain from said secondchannel;

said second inlet and second outlet being provided spaced apart fromeach other along a length of the gutter such that water entering saidsecond channel via said second inlet passes through said channel to saidsecond outlet.

The gutter may comprise at least one insert member located between saidfloor and said cover, said insert member having a cross sectional areain a direction perpendicular to its main length which varies betweenfirst and second ends of said insert member.

Preferably, the gutter comprises a pair of insert members locatedbetween said floor and said cover, at least one of said insert membersbeing tapered, wherein said channel is positioned between said pair ofinsert members.

According to a third aspect there is provided a gutter system comprises:a first elongate covered channel member capable of carrying liquid flowin a first direction; at least a second elongate covered channel memberpositioned above or below said first elongate covered channel, capableof transporting liquid in a same said direction of liquid flow.

Preferably the first elongate covered channel member has at least oneimpermeable three dimensional member located at a side of an inner wallof said channel member to form a channel within said first elongatecovered channel member which increases in cross section from said firstend to said second end.

Preferably the second elongate covered channel member has at least oneimpermeable three dimensional member located at a side of an inner wallof said channel member to form a channel within said second elongatecovered channel member which increases in cross section from said firstend to said second end.

Preferably said first elongate covered channel member has a first endand a second end, said second end defined by a water outlet.

Preferably said at least second elongate covered channel member has afirst end and a second end, said second end defined by a water outlet.

Preferably the said system gutter system comprises at least one elongatetrough for receiving and transporting liquids to said first and said atleast second elongate covered channel member.

Preferably said at least one elongate trough comprises at least oneliquid inlet.

Preferably said at least one liquid inlet comprises debris guard vortexreducing means.

Preferably the said first elongate covered channel member has a channelwidth that is substantially constant throughout the length of the saidchannel member.

Preferably the second elongate covered channel member has a channelwidth that is substantially constant throughout the length of the saidchannel member.

Other aspects are as recited in the claims herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect, there will now be described by way of exampleonly, specific embodiments, methods and processes according to thepresent invention with reference to the accompanying drawings in which:

FIG. 1 is a diagram of a simple gravity based gutter system as known inthe art;

FIG. 2 shows schematically a siphonic gutter system which is known inthe art;

FIG. 3 shows in schematic view, a known siphonic drainage system asdisclosed in WO 2007/080380;

FIG. 4 shows schematically in view from above a roof fitted with a knowngutter system, as disclosed in international patent application WO2007/080380 depicting direction of water flow along the gutters;

FIG. 5 shows a diagrammatic view of a novel drainage system according toone specific embodiment of the present invention;

FIG. 6 shows in cut away view, the drainage system of FIG. 5 herein;

FIG. 7 shows schematically the part of drainage system of FIGS. 5 and 6in cut away view from above;

FIG. 8 shows a partial view from one end of the drainage system of FIGS.5 to 7, showing an elongate cavity containing a channel and with theincorporation of a pair of three dimensional impermeable insert members;

FIG. 9 shows schematically from above a roof fitted with a plurality ofnovel gutters as described in FIGS. 5 to 8 herein, illustrating thedirection of water flow within the gutters to drainage points positionedat outside walls of a building;

FIG. 10 illustrates schematically in view from above first and secondgutter sections abutting each other for forming a joint.

FIG. 11 illustrates schematically in cut away view from one side, thefirst and second gutter sections of FIG. 10 during joint formation;

FIG. 12 illustrates schematically the first and second gutter sectionsof FIGS. 10 and 11 during a second stage of joint formation;

FIG. 13 shows in cut away view from one end the gutter under a firstlevel of rain fall in which a first enclosed channel drains water fromthe gutter;

FIG. 14 shows schematically in cut away view from one end, the gutter ofFIG. 13, under an increased level of rain fall in which first and secondenclosed channels drain rain fall;

FIG. 15 shows schematically in view from above a further embodimentgutter, having a plurality of in line water inlets;

FIG. 16 shows schematically in cut away view from one side across across section X-X′ the gutter of FIG. 15 herein;

FIG. 17 shows schematically in plan view, a first water inlet having aleaf guard/debris guard vortex reducing means;

FIG. 18 shows in cross section view from one side the water inlet ofFIG. 17 herein;

FIG. 19 shows in partial cut away view from one side, a part of thewater inlet of FIGS. 17 and 18 herein;

FIG. 20 shows in view from above a second water inlet having a debrisguard vortex reducing means; and

FIG. 21 shows schematically in cross section view from one side, thesecond water inlet of FIG. 20 herein.

DETAILED DESCRIPTION

There will now be described by way of example a specific modecontemplated by the inventors. In the following description numerousspecific details are set forth in order to provide a thoroughunderstanding. It will be apparent however, to one skilled in the art,that the present invention may be practiced without limitation to thesespecific details. In other instances, well known methods and structureshave not been described in detail so as not to unnecessarily obscure thedescription.

Referring to FIGS. 5 and 6 herein, in one preferred embodiment of theinvention, a rainwater collection system comprises a gutter section(500) and a plurality of down pipes (501, 502) positioned at one end ofthe gutter section.

The gutter section (500) comprises an elongate trough member 501 forcollecting water, said trough member comprising an elongate floorportion (502) which extends along a full length of the trough, a firstupright side wall (503) extending along the whole length of the floorportion (502) and positioned on one side of the floor portion, a secondupright side wall member (504) positioned on an opposite side of thefloor member to the first side wall (503), and extending substantiallyin parallel with the first side wall member, the floor member and firstand second upright side wall members preferably being formed in onepiece so as to be inherently water tight; a first cover portion (505)positioned above the first floor portion and extending across the fullwidth of the gutter between the first and second side walls andextending substantially in parallel with the first floor portion so asto form a first cavity (506) bounded by the first floor portion (502),the first side wall (503), the second side wall (504) and the firstcover portion (505), the first cavity being enclosed by the side wallsand first cover portion; a second cover portion (507), the second coverportion extending fully across a width of the gutter between the firstand second side walls, so as to enclose a second cavity (508) bounded bythe first cover portion (505), the second cover portion (507), the firstside wall and the second side wall; at least one first water inlet (509)which provides a passage from above the second cover (507) into thefirst cavity (506); at least one second water inlet (510) which provideswater passage from above the second cover portion (507) into the secondcavity (508); at least one first outlet aperture (511) positioned in thefirst floor member, for draining water from the first cavity into atleast one first down pipe (512); at least one second aperture (513)positioned in the first cover member (505) for draining water from thesecond cavity (508) into at least one second down pipe (514).

The first cavity (506) has a substantially trapezoidal shaped crosssection as viewed in a direction along a main length of the guttersection. Similarly, the second cavity (508), which is bounded by thefirst cover portion (505), second cover portion (507), and the first andsecond sides (503, 504) respectively, has a second substantiallytrapezoidal cross section as viewed in a direction along a main lengthof the gutter.

At least one first inlet (509) comprises a substantially circular orsquare plate which is spaced apart from and positioned above the secondcover member (507), the substantially circular or square plate having aplurality of downwardly projecting arms (515), which collectively act asa grille to prevent any leaves, twigs or debris entering into the firstwater inlet and into the first water channel (506), and allowing onlythe passage of water. The at least one first water outlet (509) ispositioned such that a plurality of apertures between the arms drainwater from a position immediately on the upper surface of the secondcover member (507), so that water collected in the gutter on top of thesecond cover member (507) flows through the first water inlet (509) intothe first water channel (506). At least one second water inlet (510)comprises a tubular upright portion (516) on top of which is provided acircular plate (517) spaced apart from an upper edge of the tubularportion (516), and between the upper rim of the tube (516) and thecircular plate, are positioned a plurality of radially extending arms(517), which hold the circular plate above the tube (516), there beingprovided a plurality of apertures between successive ones of theradially extending arms, which allow inlet of water to the second waterinlet, whilst at the same time blocking debris such as leaves, twigs orthe like which may have collected in the gutter on the upper surface ofthe second cover member (507).

Within the first cavity are provided one or preferably a plurality ofelongate water impervious tapered insert members which define a firstwater channel within the first cavity. Whilst the first cavity may havea substantially constant cross sectional area along its full length, thefirst channel defined by the space between the floor 502, first cover505 and the first and second insert members, has a gradually andlinearly increasing cross sectional area in a direction substantiallyperpendicular to the main length of the gutter.

Similarly, the second cavity encloses one or more tapered insert memberswhich define a second water channel, the second water channel having agradually increasing cross sectional area towards the outlet end of thesecond cavity. The cross sectional areas of the first and secondchannels, in the best mode, are each substantially rectangular, with thewidth of the rectangular cross section increasing linearly towards theoutlet end of each respective cavity, and increasing in the direction ofwater flow, so that water entering each channel experiences a wideningchannel as it flows along the gutter towards the outlet of therespective channel.

The first channel may be configured as a primary channel, that is achannel which under normal rainfall conditions will carry the water fromthe adjacent roof to a drainage point, and the second channel may bedesigned as a secondary channel which only comes into operation underhigh level of rainfall. For example the gutter may be designed such thatthe secondary channel only comes into operation during stage two of acategory 3 severity or above rainstorm, as set out in BSEN12056.

Thus, the gutter has a plurality of enclosed channels, one on top of theother, and an open channel on top of the enclosed channels. Watercollects in the open channel and drains into one or both of the enclosedchannels.

The gutter can be formed from any material known in the art that issuitable and commonly used within the building trade. Preferably thegutter is formed from extruded plastic or aluminum. At least oneperforation is present at various points in the trough floor(s) to formwater inlets. The water inlets allow rainwater to be transported to anyone of the water transport channels (506 and 508). The direction ofwater flow is shown as arrowed (519) in FIG. 5.

The exact water transport channel that water enters at any oneparticular time is dependent on the height of the corresponding waterinlet compared with the water level in the upper part of the trough. Ascan be ascertained by FIG. 6, in one embodiment of the invention, onewater inlet (510) is manufactured to be higher from the upper floor ofthe trough than the other water inlet (509). When water enters thetrough, water will firstly channel through the lower water inlet (509)and into first elongate covered channel (506). Water runs along thefirst channel and out of first water outlet (511), down a downpipe andthen into a drainage system (not shown). If the water flow increases andthe water level in the trough rises to a level at or above the higherwater inlet (510), then water will then additionally proceed to flowinto the second water inlet (510) and into second elongate coveredchannel (508) and down second water outlet (513) and out of the guttersystem via a second downpipe and drainage system (not shown).

The water inlets (e.g. 509 and 510) can be produced in various differentways to increase flow rate and efficiency. In one preferred embodiment,the water inlet would comprise a baffle plate as a means to reducevortex formation in and around the inlet. Vortex formation isdetrimental to the flow rate of a system because it allows air to enterthe channel and decreasing vortex formation is therefore advantageous increating a siphonic effect.

A further embodiment would be to produce a water inlet as a bowl shape.The bowl shape itself would be in the form of an inverted hollow pyramidwith a hole at the bottom to allow water flow. This configuration isknown in the art to reduce vortex formation.

However, having individual siphonic inlets is not essential to operationof the gutter system, since the diverging shape of the internal channelsof the gutter system themselves encourage the creation of a siphoniceffect in the gutter system as a whole. Therefore, non-siphonic inlets,which allow both water and air into the channels may be provided, andthe gutter system will still operate siphonically without the need forindividual siphonic inlets, since a siphonic effect begins to form withincreasing water flow rate at the downpipes, and the position offormation of the siphonic flow moves back along the channels towards theinlets, as the amount of water passing through the channel increases.

A yet further embodiment may comprise a grill or a mesh-type structureto substantially cover the water inlet. This would advantageous toprevent large objects from entering the system causing a blockage.

The water may flow through the gutter system in either a gravitydependent manner or in a siphonic water flow. In a preferred embodiment,water will initially flow into first elongate covered channel (506) andwill fall down the first water outlet (511, 512) under gravitationalpull. However, as the channel becomes full with water, the first channelwill become void of air. The action of the channel becoming full andwater dropping down the downpipe will cause a negative pressure to formwithin the channels and pipework. This negative pressure will causewater to be sucked along the elongate covered channel member, which willthus increase the water flow.

At full design capacity, the water builds up around first inlet (509),first channel (506) becomes full of water, and although workingsiphonically, reaches its maximum capacity. Water builds up in the topof the trough on top of the second cover (507) and raises to a depthwhereby it can flow over the top of the upright tube (516) of the secondwater inlet (518) and into the second water inlet.

The second channel (508) fills up similarly as the first channel (506).Initially, at low water flow rates the channel operates as a normaldrain with the water flowing under force of gravity. However, as thechannel fills up with water the channel begins to act in a siphonicmanner, with the volume of water in the second down pipe (514) causingnegative pressure which draws more water into the channel at the secondinlet (518). When the second channel is full of water and the seconddown pipe (518) is full of water, the channel operates at its fullsiphonic rate of flow, with water being drawn in through the secondinlet (518) at a relatively high rate.

From above, when fitted, the gutter may visually resemble a conventionalgutter, since only the upper cover can be seen, which presents an opentrough with one or a pair of drain points.

Referring to FIG. 7 herein, the diagram shows in plain view a preferredembodiment of an elongate channel member (700) where the first andsecond covers have been omitted. The figure shows a pair of threedimensional impermeable blocks (701, 702), which may be inserted oneither or both sides of the side walls of an elongate channel member.Each three dimensional block is tapered so as to produce a continuouslyvariable channel cross sectional area where the cross-section of thechannel increases from a first end (703) to a second end (704), wherethe second end is defined as being the end at which at least one wateroutlet is provided, and being the end towards which the water flows. Themanipulation of channel size in varying degrees along an elongatecovered channel member is advantageous, as by allowing for a narrowcross section in the vicinity of a water inlet, this increases theability of the system to run under siphonic conditions as the volume ofwater entering the elongate covered channel member will fill a narrowedchannel rendering it void of air at a lower water than if the channelwas wide.

Also shown in FIG. 7 are a plurality of optional locating straps 705-707which extend across the channel to locate the insert members in spacedapart relationship to each other. The straps each comprise a PVC coatedrigid steel strap or similar having a pair of downward pointing endswhich can be pressed into the inserts to retain the inserts in position,without obstructing the channel.

Referring to FIG. 8 herein, there is illustrated schematically in viewfrom one end, a gutter as described with reference to FIGS. 5 to 7 inpartially assembled view. Water channel (506) is defined between thefirst and second tapered insert blocks (701, 702) respectively. Thetapered insert blocks are preferably made of a high-density foam, whichis both light and durable and can easily be shaped into a tapered formby moulding or by cutting from a larger sheet of material. Preferably,the tapered members are made from sheets of relatively dense Isocyanateor poly-isobutalene, or mechanically similar equivalent foam, which arewater impervious, have high thermal insulation properties and have atleast a 25 year operational life span without significant degradation ofperformance.

In the embodiment shown, the channel (506) has a constant height, andexpands in width at a constant rate between the inlet end (705) and thedrain end (704), with the wider channel portion being positioned at thedrain end of the gutter. As the water enters the channel at the inletend (704), water flows down the channel and experiences an increasinglywider channel, of continuously increasing cross sectional area as viewedin a direction perpendicular to the main length of the gutter, with thecross sectional area and width of the channel increasing lineallytowards the drain end of the gutter.

FIG. 9 herein, shows the water flow of the present embodiment of thegutter system where a plurality of gutters are installed in a roof of abuilding. Where referring to FIG. 4 b, prior art systems have disclosedtwo water transport channels for gutter assemblies where the water flowin each channel travels in opposite directions this is disadvantageousas it means that water outlets, downpipes and drainage entry positionshave to be located within a building. When a building face is long i.e.over 200 metres, therefore two or more gutter systems may need to beintroduced on one face which gives rise to multiple positions wheredownpipes, water outlets and drainage entry positions would be needed.

The water flow in each covered channel member would flow in the samedirection (901 or 902) in any single gutter system and the channelswould sit above or below one another. Thus the number of positionsneeded for downpipes 903, 904, water outlets and drainage entry pointsis significantly reduced. Moreover all water flow could be directed tothe outer edges of the building faces, thus causing less obstruction dueto down pipes, and underground systems within the building.

Referring to FIGS. 10 to 12 herein, a method of manufacture andinstallation of the gutter system will now be described.

Firstly, having assessed the area of roof to be drained, and thepositions of available drainage points, and the specification of thegutter, i.e. the maximum amount of rainfall that the system is to copewith, the length and design of the gutter is determined using computermodelling to optimise the performance of the gutter. An overall lengthof gutter is determined, and an optimum number of individual guttersections is determined, to be joined together to provide the fullyassembled gutter, together with the widths and profiles of the channels,number and positioning of the inlets, and specifications for inlet typesand heights, and downpipe diameters and lengths. A computer modelcalculates at each position along the length of the gutter, the optimumcross sectional area of the channel, the volume of water per second atvarious fill levels of the channel, under siphonic and non siphonicmodes, and the negative pressure in the channel. The data for theoptimum channel cross sectional area can be converted to a program datafor a laser cutting machine to cut the tapered inserts to the optimumtapering profile, which could be linear, or a stepped or curved taperingshape, to provide an optimum channel shape in the trough. Preferably,the channels are shaped such that at the slowest part of the channel,which is usually the part furthest from the outlet, the speed of waterflow is always at least 0.7 metres per second, because water travellingat this speed is makes the channel self cleansing of debris, mould etc.Preferably, the system is designed to operate at negative pressures ofless than 8 metres of water to obtain reliably predictable performance.

Each run of gutter, for example, a 150-metre long run may bemanufactured in a factory as a plurality of shorter sections, to beassembled on site. Each section of gutter comprises a trough component,a first cover component, optionally, a second cover component, and foreach cover component, a corresponding one or pair of respective foamtapered insert members as described herein before. For systems designedto accommodate a category 3 or greater rainstorm, the first and secondcover members will be fitted at the factory so as to provide a two-tierchannel system. However, for systems which are designed for a category 1or 2 storm, the gutter may have a single tier enclosed channel.

In the factory, lengths of steel, aluminium or plastic are formed into atrough shape as described herein before with reference to FIG. 5onwards. Metal upright spacers may be welded across the trough atperiodic intervals to support the first cover, and/or the second cover,at a predetermined design height above the floor of the trough. Forexample the heights of the first cover may be set at 40 mm, 60 mm, or 80mm from the trough floor to provide the correct optimum design heightsof the first and second covers, to achieve the optimum channel heights.

Sheets of foam or similar are cut to a shape corresponding to thecorrect taper for the particular section of gutter being made, and areglued, adhered or otherwise secured inside the trough. In one method,the tapered insert members may be secured in the channels by a pluralityof upright spikes or pins welded to the trough floor or side walls. Inanother method, the inserts may be positioned in the troughs, and aplurality of PVC coated steel or aluminum straps may be pressed into thefoam inserts. The straps may comprise a horizontal part and twodownwardly projecting parts, one at each side which may be positionedabove the foam insert members, as shown in FIG. 7 herein, to locate thefoam tapered blocks each side of the channel. The first cover member isthen placed over the trough to form a lid to a cavity containing theinsert members and the channel. The edges of the first cover member arewelded or otherwise fixed in a watertight manner to the up right sidesof the trough, thereby enclosing the cavity and the channel, the coverforming both an airtight and watertight lid to the cavity.

The cover members are preferably made of 1.2 mm sheet steel, aluminiumor plastic with or without a plastics coating, which enables the coverto be joined to the edges of the trough using a heat weld, or a PVCsealant giving a watertight and airtight seal.

The sections of gutter at the inlet end and the drain end have aperturescut for the inlet and outlet respectively at the factory, althoughcutting of the apertures may also be possible at the installation site.The section of gutter at the outlet end may have an initial section ofdown pipe factory fitted with a watertight seal, for connection of adown pipe on site.

For the section of channel at the inlet end, cover grills as shown inFIG. 6 herein are fitted to the inlet apertures for the first channeland (where fitted) the second channel. These are preferably factoryfitted prior to shipping, but could alternatively be fitted at theinstallation site.

In the case of a two tier gutter system, in the factory a further set offoam insert members are cut to shape and fixed on top of the first covermember, similarly as herein before described for the first channel, andabove which is fitted a second cover member. The second cover member iswelded, heat sealed or otherwise adhered to the upright sides of thetrough member to ensure a watertight seal.

The individual gutter sections are transported to the site, and arelifted on to the roof either manually, or using a crane. The guttersections are bolted in place at the edges of the roof and/or to theframe of the building, and in the case of a building having a multipleapex roof, in the valleys between the roof sections.

Referring to FIG. 10 herein, there is shown schematically in view fromabove the ends of two gutter sections 1000, 1001 positioned end to endfor joining on site.

As shown in FIGS. 10 to 12, the ends of the gutter sections aremanufactured such that a portion of the floor of the trough is exposedand accessible from above, and the first and second cover portions arestepped with respect to each other, to allow access to the joint forconnecting the gutter sections on site.

Referring to FIG. 10 herein, there is shown in view from above a firststage of joining two gutter sections 1000, 1001. Each gutter section hasits upper and mid covers, 1002, 1003 respectively, exposed and extendingshort of the end of the gutter section. The ends of the trough areabutted together. Shown are the protruding ends of the foam inserts1004, 1005 of the upper and lower cavities respectively, which in thisexample protrude from the ends of their respective cover members, so asto allow a platform across which to span a further section of cover overthe joint.

Referring to FIG. 10 herein, there is shown the first and second guttermembers (900, 901 respectively) of FIG. 9 herein, in cut away view fromone side during a jointing operation. The first and second guttersections (900, 901) are placed abutting each other end to end. Eachsection is supplied from the factory with the first and (where fitted)second cover members cut slightly short of the end of the gutter, toleave room for creating a joint between the ends of the two gutters. Thetwo gutters are placed end to end and are fixed in place to the roof oradjoining building structure. To create a joint, a plastics membraneand/or tape strips 1004 may be fitted either inside the trough membersand/or outside the trough members and heat sealed to create a watertightseal. Additionally, the two ends of the gutter may be bolted together attheir ends with one or a plurality of plates (1003) extending across thejoint. A plurality of optional waterproof stick pins 1100 may protrudeupwardly to locate the tapered foam inserts which are pressed down intopositions across the joint.

Referring to FIG. 12 herein, one or a pair of insert members (1200),which are pre-cut to shape in the factory, or which can be cut fromblock of foam material on site, are inserted across the joint in orderto provide continuity of the tapered insert members on one or eitherside of the channel as appropriate. Once the inserts (1200) are fixed inplace, a first section of cover (1201), which is preferably pre-cut toshape in the factory, or which can be cut to exact size on site is laidacross the trough and across the joint, and is heat welded, taped,sealed or otherwise joined in a watertight manner to the two lengths offirst cover member either side on each gutter section, thereby enclosingthe joint around the first (lower) channel in a watertight and airtightmanner.

Joining of the second cavity and second channel across the joint betweengutter sections is similarly carried out with a further one or moreblocks of insert member cut to shape and size to provide continuity ofthe second channel shape, and a further cover section being welded orglued in place over the second channel and between the upper (second)cover portions of each gutter section, thereby creating a watertight andairtight seal.

The most important joint to make is the joint between the abuttingtrough members, since this is the joint which keeps the water out of thebuilding. The other joints on the cover members are preferably watertight and airtight to promote negative pressure in the channel and thesiphonic behaviour, but if there is some degree of leakage on thesejoints, it is not critical since it only marginally affects the siphonicbehaviour, and there is no risk of water leaking into the building.Under conditions of heavy rainfall, since the upper open channel will befull of water, then any minor leaks between channels through the coverjoints will not significantly affect siphonic operation since only waterwill pass though the leaks.

Referring to FIG. 13 herein, there is illustrated schematically in crosssectional view from one end operation of the gutter system of FIGS. 5 to12 herein under conditions of moderate rain fall. Under conditions ofmoderate rain fall, for example a category 1 or category 2 shower, watercollects on top of the upper cover member and flows into the first inlet509), along the first channel (506) and down the first outlet (511) intofirst downpipe (512). As the water fills up above the top of the firstinlet and flows into the inlet to the first channel (515), and as thefirst channel (506) fills up with water, the shape of the graduallyexpanding first channel towards the outlet creates a negative pressureand siphonic operation of the channel begins, which sucks water down thefirst inlet (509) at an increasing rate until the first channel isoperating fully siphonically. It is important that the channel iswatertight and airtight along its length except for the inlets andoutlets, to avoid air entering the first channel and reducing thesiphonic effect caused by reduced pressure in the channel.

At this level of rainfall, because the water level in the top part ofthe trough is below the water intake level of the second inlet (510),little or no water enters the second inlet (510) and the second channel(508) remains unused.

As shown in FIG. 14 herein, under conditions of increased rain fall, forexample a category 3 storm, water fills up in the top part of the gutterabove the levels at which both the first inlet (509) and the secondinlet (510) can intake water. Under these conditions, the first channel(506) is filled with water and operates siphonically, and water alsoenters the second inlet (510) and the second channel (508). Both thefirst and second channels fill with water, and the second channel alsobegins to operate siphonically.

The rain fall rate at which the first and second channels begin toaccept water is a design selectable parameter, by altering the height ofthe first and second inlets (510) above the upper cover. At one extreme,the inlet of the second channel can be placed at the same height as theinlet of the first channel, in which case the first and second channelsmay drain water at a similar rate as each other and operate in parallel,whatever the level of rain fall, and the onset of siphonic operation mayoccur at approximately the same time for each channel.

Alternatively, the second inlet (510) may be raised above the firstinlet, so that the water level builds up in the upper part of the troughto such a level that the first channel is operating fully siphonicallybefore any water enters the second inlet, and therefore the secondchannel operates as an overflow channel only.

Alternatively, by placing the height of the first inlet higher than theheight of the second inlet, the roles of the two channels may bereversed, so that the upper channel acts as the primary channel forlower levels of rainfall, and the lower channel acts as the secondary oroverflow channel.

Further, the diameter and/or area of the inlets and outlets may bevaried as a design parameter to affect the rate of water flow throughthe inlets and outlets. In the example shown in FIGS. 12 and 13, theoutlet of the first channel has a slightly larger diameter and is fittedto a slightly large diameter down pipe than the outlet (513) of thesecond channel.

Referring to FIG. 15 herein, there is illustrated schematically in viewfrom above a further embodiment gutter in plan view, showing a pluralityof water inlets 1500, 1501 along the length of the upper open channelfor accepting water in to the first (primary) enclosed channel; a secondplurality of inlets 1502, 1503 for accepting water from the upper openchannel in to a secondary enclosed channel. In this case, the inlets arepositioned in line along the length of the upper open channel, but inother embodiments, the inlets to the primary and secondary channel couldbe staggered, or placed side to side. Similarly, a first and secondoutlets 1504, 1505 to the primary and secondary channels respectivelymay be positioned length wise along the gutter, or may be placed side byside at the end of the gutter.

A plurality of inlets corresponding to each of the primary and secondarychannels may be provided at various distances along the length of thegutter. The inlets may each comprise a debris guard vortex reducingmeans, or may simply be provided with a grill in order to prevent leavesor debris entering the primary and secondary channels.

Referring to FIG. 16 herein, there is illustrated schematically in cutaway view from one side, a cross section X-X′ of the further embodimentgutter of FIG. 15 herein. Shown are a plurality of relatively lowerheight water inlets 1500, 1501 and a plurality of relatively higherlevel water inlets 1502, 1503. The lower level inlets admit water to afirst, lower enclosed channel, and the higher level inlets admit waterto a second, upper mid level enclosed channel. Both the first and secondinlets drain water from an upper level open channel, in to which watercollects from a roof structure on either one or both sides of thegutter. The lower level enclosed channel exclusively drains water fromthe upper open channel, up until a point when the water level in theopen upper channel reaches the height of the second inlets 1502, 1503 atwhich point the second enclosed channel begins to operate in parallel tothe first enclosed channel, to drain water from the open upper channel,At this stage all water inlets are draining from the open upper channel.

Referring to FIG. 17 herein, there is illustrated schematically in viewfrom above a first embodiment water inlet cover, incorporating a debrisguard vortex reducing means. The first water inlet cover may be used tocover the inlets of the first and/or second enclosed channels of thenovel gutter systems as disclosed herein, or may be used in knowndrainage systems such as gravity fed drainage systems, or as a waterinlet cover for existing already installed legacy siphonic drainagesystems incorporating siphonic bowls.

The inlet comprises a substantially circular central plate 1700,surrounded, at a perimeter thereof by a plurality of radially extendingarms 1701, substantially equidistantly spaced apart around the perimeterof the plate 1700; a first substantially circular ridge portion 1702connecting the plurality of arms 1701; and a second substantiallycircular connecting ring member 1703 which connects the outer ends ofthe outwardly extending arms. The central plate 1700 comprises one or aplurality of apertures 1704 which enable the inlet cover to be fixed,for example by bolts, to either a tubular inlet pipe, a siphonic bowl,or a conventional gravity down pipe.

The plurality of inner arm portions 1705 define a plurality of innerapertures 1707 which face inwardly towards the centre of the platemember 1700, arranged around the plate member in a circle. Each inneraperture is defined by a perimeter of the plate, a pair of adjacentarms, and the upper ring member 1702.

The plurality of outer arm portion 1706 define a second set ofapertures, which face outwardly from the centre of the water inlet, eachaperture defined an adjacent pair of outer arm portion 1706, at an upperend by the inner circular connecting member 1702, and at a lower end bythe outer circular connecting member 1703.

An upwardly facing surface of the plate 1700 comprises a shallow domeshape, such that water entering inside the upper ring 1702 and restingon the dome flows in a direction outwardly towards the inner apertures1707.

The water inlet cover comprises two main functional parts. Firstly, thecentral plate member acts to exclude air from entering the downpipe orbowl (depending on which type of rainwater system the inlet cover isfitted to) during high flow conditions. Excluding air from immediatelyabove the centre of the pipe or bowl promotes a greater water flow andcan encourage the onset of siphonic behaviour.

Secondly, the radially extending arms act as an outer grill whichprevents debris over a particular size from entering the inlet, sincethe debris (primarily leaves, but also including items of litter roofingmaterials such as bolts, or roof panel fragments etc.) from entering thedrainage system. The arms create a ridged grill consisting of grillmembers (the arms) with a plurality of apertures there between. Theridged shape of the arms tens to keep the debris on the outer perimeterof the inlet cover under lower and moderate levels of water flow, as thedebris cannot pass over the top of the ridge into the centre of thecover.

Referring to FIG. 18 herein, there is illustrated schematically in cutaway view from one side, the inlet cover of FIG. 17, along the lineY-Y′. Each arm 1701 comprises an inner inclined section 1705 extendingbetween a perimeter of the central plate member and the inner connectingring 1702, and a second inclined portion 1706 extending between theinner connecting ring 1702 and the outer connecting ring 1703. The innerinclined arm portion 1705 is arranged so as to be relatively shortercompared to the outer inclined portion 1706, an upper end of the innerinclined arm portion meeting an upper end of the outer inclined armportion 1706 at the position of the inner ring member 1702. As viewed incut away profile, the arm portion is of a substantially inverted “V”shape having a relatively longer outer arm portion, so that the armresembles a spider leg arrangement.

In a modified embodiment, the outer ring member 1703 may be omitted, sothat the lower ends of each outer arm portion 1706 are unconnected toeach other. The substantially circular plate member 1700, viewed incross section from one side comprises a smooth underside.

Referring to FIG. 19 herein, there is shown in partial cut away viewfrom on side a single arm of the inlet cover of FIGS. 17 and 18 herein,showing the peaked inverted “V” shape of the arm, and the connectingridge portion 1702. Debris collects preferentially on the outside of thearm, at the longer length of the arm in preference to inside the ring1702 due to the overall crater like shape of the cover, and the ridgedgrill formed by the arms.

Referring to FIG. 20 herein, there is illustrated schematically a secondwater inlet cover. The second water inlet cover comprises asubstantially square plate member 2000; a plurality of outwardlyextending arm members 2001 arranged peripherally around an outerperimeter of the plate member 2000; a plurality of apertures 2002positioned on the plate 2000 for attaching the water inlet to a drainpipe, water inlet tube, or siphonic inlet bowl; a connecting ring 2003which connects together an upper portion of the plurality of radiallyextending arms 2001, and which surrounds and is spaced apart from thecentrally located plate 2000; and a plurality of annular locating rings2004, each of which is located at a lower end of a correspondingrespective radially extending arm, for securing the cover to a surfaceof a gutter, around an inlet aperture.

Each radially extending arm has a relatively shorter upright innerportion, and a relatively longer upright outer portion, similarly asshown with reference to FIG. 19 herein, but without the lower ends ofthe arms being connected by a lower connecting ring (although in yetanother variation of the second inlet cover, the lower arms could beconnected to each other). The plurality of radially extending armsdefine a plurality of inwardly facing apertures 2005 through which waterwhich collects inside the ring 2003 can drain from the plate and in toan underlying drain pipe or collecting bowl. The outer portions of theradially extending arms define there between a plurality of outwardlyfacing apertures, through which water can drain from a position outsideof the inlet cover, for example water collecting on a flat surface of agutter channel, and which can drain through the outer apertures in tothe underlying rain water collection pipe, enclosed channel or siphonicbowl.

Referring to FIG. 21 herein, there is shown schematically the secondinlet cover of FIG. 20, in cut away cross sectional view along the lineZ-Z′.

Each arm has an inner upright portion and an outer upright portion,connected at an upper ridge 2102, so that the plate member 2000 forms acrater floor shape inside the ring of arms, with the peripheral ridgeformed by the plurality of peripheral radially extending arms.Individual ones of the arms have an annular molding 2004 containing anaperture, by means of which the inlet cover may be bolted or screwed toa flat surface around an inlet.

In use, operation of the first and second inlets is very similar, and asfollows. Under moderate water flows, water encountering the inlet willflow between the outer apertures and down in to the rain watercollection pipe or collection bowl underneath. Any debris such asleaves, twigs or litter will be prevented from flowing in to the drainby the outwardly extending arms. However, the leaves, litter and debrismay still lie across the apertures, which means that further debris andstanding water may build up behind the leaves and debris. Water flowingover the leaves and debris may flow over the top of the ridge and thering connecting member, and in to the centre of the “crater” surroundedby the ridge. Water entering the centre of the inlet will flow outwardlytowards the inner apertures, and down in to the rain water pipe orcollection bowl. Clearly, if there is enough debris, litter or leavessuch that the inlet is completely blocked with debris, then having bothan outwardly facing and an inwardly facing sets of apertures will notprevent blockages and the inlet cover becoming blocked altogether.However under less extreme volumes of debris, debris will bepreferentially retained outside the centre of the crater, leaving theinner apertures unobstructed and capable of draining water.

Where the inlet cover is fitted directly to a gutter floor, ove anaperture in the gutter floor, an upper surface of the plate ispositioned at a height above a height of an outer perimeter of saidcover, such that when the cover is fitted to a gutter floor, the platelies substantially parallel to, and above a level of said gutter floor.In various modifications to the embodiments, the inlet cover may bedesigned to be vortex preventing, or not. Where a simple flat, circularor flat rectangular plate is provided with a flat underside then vortexprevention may be left un-optimised. However, where the shape of theinner circular or square plate is domed on the upper surface, andprovides a convex cusp shaped protrusion in the centre, this mayeffectively exclude air in the waterflow under high flow conditions, andaid the prevention of vortices.

It will be appreciated by the skilled person that the embodiments ofFIGS. 17 to 21 may be formed in a variety of ways, such as by plasticsmouldings, or as a metal casting. In other embodiments, the surroundinggrill barrier may be formed from wire mesh shaped into a ridged ring.

A further advantage of the specific embodiments disclosed herein is thatusing a same trough width and cover width, the widths and the crosssectional areas of the internal channels can be varied over a range tooptimise the onset of siphonic behaviour gutter to different roof areasand designed for rainfall rates using a single set of trough and coverdimensions, by inserting different widths of tapered insert member. Thesystem can be designed to meet various different levels of rain fall androof area, using the same trough second and cover members, with thedesign changes occurring only on the foam inserts, the diameters and/orcross sectional areas of the inlets and outlets, and the relativeheights of the first and second inlets. This has the advantage ofstandardising components for the trough and covers and thereby reducingoverall system costs by avoiding the need to manufacture differenttrough and cover sizes. Optimisation of the water flow rates, sizes ofinlet and outlet apertures, and the shape and cross sectional area ofthe internal channels at each position along the channel can bedetermined by computer implemented calculations, to give an optimumdesigned system for each building, roof area and climate. Both theheight and the width of the channels are design parameters which can beeasily varied, by use of different height vertical spacers and differentwidth or shaped insert members, using a single trough shape.

Specific embodiments disclosed herein may have an advantage ofpermitting, through the use of a multi-storey channel system, siphonicbehaviour of one or more inclined or substantially horizontal waterchannels, where each channel drains to a same end of a gutter system.Further, two such gutter systems can be placed end to end, with theiroutlet ends placed opposite to each other, and their respective inletends placed adjacent to each other so as to enable drainage of a lengthof roof of the order of 400 metres or more using siphonic guttering,without the need for any down pipes to be present in the middle of thespan between the two outlet ends of the end to end gutter lengths. Thismay avoid the need to fit drains in the centre of a building's concretefloor slab, or at least reduce the amount of such drains needed.

Further, since the internal shape of the channels promotes siphonicbehaviour in the channels themselves, there is no need for an additionalhorizontal or shallow inclined parallel pipe inside the building, as inthe prior art case shown in FIG. 2 herein. This avoids additional pipinginternal to the building, and avoids the additional jointing with itsassociated inspection and maintenance and risk of leakage inside thebuilding.

Further, conventional siphonic systems comprising lengths of pipe andsiphonic inlets as shown in FIG. 2 herein, have step changes in pipesize at every inlet, and are restricted by the available pipe diametersto a limited range of cross sectional areas of water channel in thepipe. In contrast, in the specific embodiments herein, the channel crosssectional area is continuously variable as a design parameter, allowinggreater optimisation of cross sectional area at any distance along thewater channel and enabling greater optimisation of the water flow.Whereas conventional pipe based siphonic systems are designed to beoptimised around a single rainfall rate, and the pipe sizes are fixedonce installed, this means that the conventional systems may not performoptimally at other ranges of rainfall, foe example 60% of “design for”rainfall rate. In contrast, the embodiments presented herein have acontinuously tapered channel cross section and can therefore be designedfor optimised performance over a range of rainfall rates, rather thanjust one target rainfall rate, because they are not restricted bypredetermined pipe sizes. The embodiments described herein may bedesigned to operate siphonically over a greater range of rainfall ratesthan a known pipe based siphonic drainage system, and can be designed tobecome siphonic at a large range of fill levels of the primary channels,compared to known pipe based siphonic systems. In turn, this means thatthe risk of overflow of the open channel which collects the rainwaterprior to entering the inlets is reduced compared to known systems,because the open upper channel is drained more quickly. This has theadvantage of reducing the risk of flood or water damage inside thebuilding due to gutter overflow compared to known systems, theoccurrence of which is often incorrectly attributed to leaking joints,resulting in unnecessary system maintenance in prior art pipe systems.

1. A gutter system comprising: a first elongate covered channel capableof carrying water flowing in a first direction; and a second elongatecovered channel positioned above said first elongate covered channel,said second channel capable of carrying water flowing in said firstdirection.
 2. The gutter system as claimed in claim 1, comprising anopen channel positioned above said first and second channels, forcollection of rainwater.
 3. The gutter system as claimed in claim 1,wherein said first and/or second channels are substantially sealed alongtheir whole lengths, except at their ends.
 4. The gutter system asclaimed in claim 1, having a channel cross sectional area which iscontinuously variable along its length.
 5. The gutter system as claimedin claim 1, wherein said first and/or second channel has a crosssectional area which increases in the direction of water flow.
 6. Thegutter system as claimed in claim 1, wherein said first and/or secondchannel is of a substantially constant height along its full length. 7.The gutter system as claimed in claim 1, wherein said first and/orsecond channel has a substantially rectangular cross sectional area in adirection perpendicular to a main length of said gutter.
 8. The guttersystem as claimed in claim 1, comprising: a first water inlet positionedat a first end of said gutter for allowing water to enter said firstchannel; a first water outlet positioned at a second end of said gutterfor draining water from said first channel; a second water inletpositioned at said first end of said gutter for allowing water to entersaid second channel; and a second water outlet positioned at said secondend of said gutter for draining said second channel.
 9. The guttersystem as claimed in claim 1, comprising a debris guard vortex reducingmeans for minimizing vortex formation in and around at least one waterinlet.
 10. A gutter system as claimed in claim 1, wherein: said firstchannel is formed within a first cavity, said first cavity having asubstantially trapezoidal cross sectional area as viewed in a directionperpendicular to a main length of said gutter; said first channel isdefined by at least one elongate tapered insert fitted inside said firstcavity; said second channel is formed within a second cavity, saidsecond cavity having a substantially trapezoidal cross sectional area asviewed in a direction perpendicular to a main length of said gutter; andsaid second channel is defined by at least one tapered insert memberfitted within said second cavity.
 11. A gutter section comprising: anelongate trough having a floor, a first elongate upright side wall and asecond elongate upright side wall; and an elongate cover member spacedapart from said floor and extending between said upright side walls, andclosing off an upper part of said trough at a first height, so as todefine an enclosed cavity there between; wherein: a single enclosedchannel being provided across said trough between said floor and saidcover member and extending along a length of said trough.
 12. The guttersection as claimed in claim 11, further comprising an open channelpositioned above said enclosed channel and defined between said firstand second side walls of said trough.
 13. The gutter section as claimedin claim 11, wherein said enclosed channel has a variable crosssectional area in a direction transverse to a main length of the guttersection.
 14. The gutter as claimed in claim 11, comprising at least oneinsert member located between said floor and said cover, said insertmember having a cross sectional area in a direction perpendicular to itsmain length which varies between first and second ends of said insertmember.
 15. The gutter as claimed in claim 11, comprising a pair ofinsert members located between said floor and said cover, at least oneof said insert members being tapered, wherein said channel is positionedbetween said pair of insert members.
 16. The gutter section as claimedin claim 11, comprising a water inlet for allowing water to enter saidenclosed channel.
 17. The gutter section as claimed in claim 11,comprising a water outlet for allowing water to drain from said enclosedchannel.
 18. The gutter section as claimed in claim 11, comprising atleast one insert member located between said floor and said cover, saidinsert member having a cross sectional area in a direction perpendicularto its main length which varies between first and second ends of saidinsert member.
 19. The gutter section as claimed in claim 11, comprisinga pair of insert members located between said floor and said cover, atleast one of said insert members being tapered, wherein said channel ispositioned between said pair of insert members.
 20. The gutter sectionas claimed in claim 11, comprising a second elongate cover memberpositioned above said first cover member, so as to define a secondcavity on top of said first cavity and running substantially paralleltherewith, between said second cover, said first cover and said firstand second upright side walls.